Preservative compositions

ABSTRACT

IN ORDER TO INCREASE THE PERMANENCY OF CHLORINATED PHENOLS (IN PARTICULAR PENTACHLOROPHENOL) IN WOOD TO WHICH THEY HAVE BEEN APPLIED AS FUNGICIDES A SALT OF CHROMIC ACID WITH AN ORGANIC BASE IS EMPLOYED TO ACT AS A FIXATIVE. PREFERABLY THE ORGANIC DICHROMATED AND THE CHLORINATED PHENOL ARE APPLIED TO THE WOOD FROM THE SAME SOLUTION IN AN ORGANIC SOLVENT.

lil 'ltisiii SR v me a 702 t a v a a 2.7 T 1 United v I 3.102.184 k iented Nov. 14 1972 more years which is a typical period for use for timber 3,702,784 used for construction purposes. Until now satisfactory PRESERVATIVE COMPOS methods for increasing the permanency of toxic agents in James G. Farquhar, Harrogate, and Geoffrey M. Gibson and Brian J. Joice, Leeds, England, assignors to Albright & Wilson Limited, Warwickshire, England No Drawing. Filed July 22, 1969, Ser. No. 843,771

Claims priority, application Great Britain, July 23, 1968,

35, 68 Int. Cl. B271! 3/00; B44d 1/26; B05c 3/(76) US. Cl. 117-149 Claims ABSTRACT OF THE DISCLOSURE In order to increase the permanency of chlorinated phenols (in particular pentachlorophenol) in wood to which they have been applied as fungicides a salt of chromic :acid with an organic base is employed to act as a fixative. Preferably the organic dichromated and the chlorinated phenol are applied to the wood from the same solution in an organic solvent.

The present invention relates to the preservation of cellulosic materials, such as wood, plywood, chipboard, hardboard and the like. Such materials are hereinafter termed woody collulosic materials. In particular it relates to techniques wherein the preservative material is applied to the substrate from an organic solvent.

It is common practice to apply substances to woody cellulosic materials which are toxic to wood boring creatures and/ or fungal growth occurring thereon from water based solutions. Such treatments, howdever, sufier the disadvantages that the water causes swelling in the cellulosic materials, so that these solutions are unsuitable for treating timbers or boards which have already been machined to a desired shape or size. Furthermore, preservative agents which are capable of being applied from a water based solution are also liable to be leached out by water. In order to combat such leaching out of the preservative agents, preservative compositions have been formulated which contain compounds in addition to the toxic agent, whose role is to assist in keeping the toxic agent in the cellulosic material. Among such compounds are the water soluble dichromates.

The use of such formulations does not, however, overcome the other main disadvantage in employing water based preservative compositions, namely the swelling caused in the substrate. In an attempt to avoid this, preservative agents such as chlorinated phenols and their salts have been applied to woody cellulosic materials from organic solvents which do not cause any swelling of the substrate. The use of such solvent-based compositions containing chlorinated phenols (which are highly toxic to certain wood pests particularly fungi) has drawbacks in that the toxic agents employed are liable to be lost from the substrate either by leaching with water if they are slightly water-soluble, or by evaporation over the course of the several years in which the substrate is used. Thus solvent based chlorinated phenol compositions have not found the degree of commercial use which might have been expected simply by considering their toxicity to certain wood pests. It should be noted that compounds with even only a very small vapour pressure will be liable to evaporate over periods of 50 or cellulosic materials have been possible with water-based formulations only.

We have now found that by incorporating chromic acid salts of organic bases, having at least one straight or branched chain containing at least 6 carbon atoms into solvent based preservative compositions, an improved permanency of chlorinated phenols and their salts in the cellulosic material may be obtained. These chromic acid salts are able to reduce or suppress, depending on their proportion in the composition, the loss of chlorinated phenols from the cellulosic materials by evaporation, especially at slightly elevated temperatures such as 50 C. They are also able to reduce the ease with which chlorinated phenols can be leached from the cellulosic materials by water. The resistance to water leaching may be further enhanced if the cellulosic material is aged at slightly elevated temperatures (for example, for 1 week at 50 C.) after impregnation with the composition. Two of the practical advantages arising from these effects are the following. Protection of woody cellulosic material initially containing the amount of chlorinated phenols normally employed will be longer-lasting, especially in hot countries, in the presence of these chromic acid salts, because the loss of preservative as time goes on will be less. For the same reason the use of concentrations of chlorinated phenols less than those normally employed will give in the presence of these chromic acid salts protection for the same length of time as would be obtained by use of more normal concentrations of chlorinated phenols in the absence of these salts, thus providing useful economies in the amount of preservative required for a given purpose.

Accordingly, from one aspect the present invention provides a process for preserving woody cellulosic materials which comprises applying to the material an organic solvent solution of a chlorinated phenol having one or more hydroxy groups bound to a benzene ring and from 1 to 5 chlorineatoms bound to the same benzene ring which is optionally substituted by one or more hydrocarbon groups or a salt of such a phenol soluble in the solvent, and a salt of chromic acid with an organic base, which is sufiiciently soluble in the solvent to provide a solution containing at least 0.2% w./v. CrO (equivalent) at 20 C. which contains at least one straight or branched chain containing at least 6 carbon atoms. The process may be carried out by applying the chlorinated phenol or its salt to the wood either in the same solution as the chromium compound, or in a different solution either before or after the application of the chromium compound.

From a second aspect the invention provides a composition suitable for the treatment of woody cellulosic materials which comprises an organic solvent having dissolved therein a chlorinated phenol as above defined or a salt thereof, and a salt of chromic acid with an organic base sufficiently soluble to provide a solution containing at least 0.2% w./v. CrO (equivalent) at 20 C. and having at least one branched or straight chain containing at least 6 carbon atoms.

Suitable salts of chromic acid with organic bases for use in the present invention are those which are sufiiciently soluble in the solvent employed to provide a solution containing at least 0.2% w./v. CrO (equivalent) at C. The preferred organic bases are those which contain branched chains, which may consist solely of carbon atoms or may also contain nitrogen atoms. Suitably the organic bases are primary, secondary and tertiary amines, quaternary ammonium bases, substituted guanidines, biguanides, and s-triazines possessing at least one branched chain in the molecule. Particularly suitable types of base are secondary and tertiary alkyl primary amines having from 6 to 22 carbon atoms in the alkyl group, in which the amino group is joined to a carbon atom which is itself attached to two or three alkyl groups, respectively. Other useful compounds are the guanidine derivatives of such amines.

Particular bases which are preferred for the present invention are Z-ethyI-n-hexyl amine, di-(Z-ethyl-n-hexyl) amine, tri-(3,5,5-trimethyl-n-hexyl) amine, the mixture of tertiary alkyl primary amines containing from twelve to fourteen carbon atoms known as Primene 81-R (the word Primene being a registered trademark), the mixture of tertiary alkyl primary amines containing from eighteen to twenty-two carbon atoms known as Primene JM-T, the mixture of secondary alkyl primary amines derived from n-undecane known as Armeen L.l1 (the word Armeen being a trademark). Other useful compounds include 2,4,6 tris-(2 ethyl n hexylarnino)-striazine the mixed 1,5-dialkyl biguanides derived from Primene" 8l-R or Primene JM-T, and the mixed, N,N',N"-trialkyl guanidines derived from Primene 81R or Primene JM-T.

The hexavalent chromium salts suitable for use in the present invention are chromates and dichromates which are frequently of the composition B H CrOl, or

respectively (where B represents one molecule of a monoacidic base).

It will be understood that salts for use in the invention include all organic base/chromic acid salts which have the appropriate solubility characteristics as defined above and that such salts can be used according to the invention either singly or in admixture with each other or one another. It will also be understood that bases which are too easily oxidised by chromic acid, and salts which too easily decompose by internal oxidation-reduction reactions, are to be avoided.

Preservative agents which are of use in the present invention are chlorinated phenols and their solvent-soluble salts. Such compounds contain one or more hydroxyl groups bound to a benzene ring and from 1 to 5, preferably 3 to 5, chlorine atoms bound to the same benzene ring. The benzene ring may however, be substituted by one or more hydrocarbon groups such as alkyl groups having from 1 to 6 carbon atoms or aromatic groups. Compounds which may be employed include the tri and tetrachloro cresols, chlorinated bis phenol A, the trichloro xylenols, tetrachloro ortho phenyl phenol and chlorinated hexyl phenols. The preferred compounds, however, are tri, tetra and penta chlorophenols, especially penta chloropheuol. When salts of chlorinated phenols are used, it is understood that they will be compatible with the chromic acid salt, as for example when the salt of the chlorinated phenol and the chromic acid salt are derived from the same organic base.

Other preservative agents commonly used in solventbased wood preservative compositions may also be included in the compositions if desired, such biocidal compounds include for example copper naphthenates, solubilised copper 8-quinolinolate and triorganotin compounds such as tributyltin oxide and its derivatives. Solvent soluble salts of arsenic acid with suitable organic bases such as #Primene 81-R and Primene J-MT may also be employed. All these materials may have their own permanency in woody cellulosic materials improved 4 when they are employed in the presence of a hexavalent chromium compound.

Suitable solvents for use according to the invention include aromatic hydrocarbons such as xylene and aromatised petroleum distillates, petroleum hydrocarbon solvents, and mixtures of petroleum hydrocarbon solvents with aromatic hydrocarbons and/or ketones. It is desirable that the solvent should either not react at all, or react only very slowly, with the chromic acid salt at temperatures of less than 30 C.

The chlorinated phenol will normally be present in an amount depending on such factors as the degree of protection and the degree of penetrability desired, and the cost of the solvent. Typically it will provide from 0.5 to 10% of the total composition. The chromic acid salts will be used in amounts which will fix substantially all of the preservative, or only a part of it, whichever may be desired. The amount required will vary according to the nature of the preservative and its own concentration in the preservative composition and the degree of fixation desired but normally will lie within the concentration range 05-50% and is often preferably in the range 12S% of the total composition.

'Cellulosic materials may be treated with the compositions as described above by any convenient method. For example, the desired composition may be applied to the wood by brushes or rollers, or the wood may be dipped int the preservative solution. A further method by which impregnation may occur is by exposing the material to be treated to a solution of desired composition under pressure, for example by evacuating a vessel containing the material, covering the material with the solution, and then restoring the pressure to atmospheric.

The compositions of the invention may also contain other substances which commonly occur in solvent-based compositions employed for the preservation of woody cellulosic materials; for example, insecticidal compounds such as lindane and anti-blooming agents (which prevent the formation of deposits of solid chlorinated phenols on the surface of the cellulosic material) such as dibutyl phthalate.

Compositions for use in the present invention are illustrated by the following examples:

EXAMPLE 1 Four preservative formulations (A, B, C and D) were prepared from the following quantities (in parts by weight) of pentachlorophenol, Primene Sl-R dichromate, and xylene, respectively: A-5,0,95; B-5,5,90; C- 5.7,88; and D5,10,85. Pinewood strips, 25 mm. x 5 mm. x 1.6 mm., were impregnated with these formulations by a simple vacuum-pressure technique. The strips were contained in a vessel, which was pumped down to a pressure of 15 mm.; of mercury. After 30 minutes of continuous pumping, the vessel was isolated from the pump, the strips were covered with one of the above formulations, and atmospheric pressure was restored. After soaking in the liquid for 2 hours, the strips were removed and allowed to drain on absorbent paper. They were then allowed to stand at the ordinary temperature until all the xylene had evaporated.

The pentachlorophenol content of the impregnated strips was determined by boiling a sample (about 0.5 gm.) with 0.1 N-sodium hydroxide (250 ml.) for 3 hours. This process extracts all the pent-achlorophenol and any unreduced hexavalent chromium from the wood. The extract was acidified and extracted with xylene, and the pentachlorophenol content of the xylene extract de termined colorimetrically by the 4-amino-antibyrine/ ferricyanide method of Goto, Kawahara and Sato (Analytical Abstracts No. 577 3 (1964)).

The remaining strips impregnated with formulations A, B, C and D were placed in an air oven at 50 C., and

kept there for 4 weeks. Samples were withdrawn at intervals during this period and their pentachlorophenol content determined by the above method. In the case of the chromium-free formulation (A) the pentachlorophenol content fell from its initial value of 71.4 mg./g., of wood to 23.5, 8.4 and mg./g., after 1, 2, and 3 weeks respectively, corresponding to pentachlorophenol evaporation losses of 67, 89, and 100% respectively. On the other hand, strips impregnated with formulation D suffered no change in the initial pentachlorophenol content of 59.2 mg./g., of wood after 1, 2, 3, and 4 weeks. The strips impregnated with formulations B and C showed intermediate behaviour. Thus with B the initial pentachlorophenol content of 64.6 mg./g., of wood had fallen to 41.4 mg./g., after 4 weeks (36% evaporation loss), whereas with C the initial 64.5 mg./g., had fallen to 53.5 mg./g., after 4 EXAMPLE 2 Pinewood strips were impregnated with formulations A and D and dried at the ordinary temperature as described in Example 1. Half of the D-strips were aged at 50 C. for 1 week, and the other half, along with the A-strips, were aged at the ordinary temperature for 6 weeks. After aging, the pentachlorophenol content of the three strips was determined as described in Example 1. About half a gram of each kind of strip was then separately stirred with 1 litre of cold water for a few days. The water was then removed, replaced by a fresh 1 litre quantity, and stirring continued for another few days. This leaching process was continued until the strips had been extracted four times. The various extracts were separately treated with an excess of sodium hydroxide, vacuum-distilled to small bulk, acidified and extracted with xylene for pentachlorophenol determination as in Example 1. The cumulative percentage of the original pentachlorophenol lost from the strips at the end of each extraction period is shown in the following table:

Cumulative percent loss of pentachlorophenol after total leaching times 01- A preservative formulation (E) was prepared from pentachlorophenol parts by weight), Z-ethyl-n-hexylamine chromate (9.4 parts), and xylene (85.6 parts). Pinewood strips were impregnated with formulations A and E, dried at the ordinary temperature, and samples analysed for their pentachlorophenol content, all as in Example 1.

The strips were placed in an air oven at 50 C., and kept there for 2 weeks. At the end of this time the pentachlorophenol content of the A-treated strips had fallen from its initial value of 71.4 mg./g., of wood to 8.4 mg./ g., corresponding to an evaporation loss of 89%, whereas in the case of the E-treated strips the fall was from 65.6 mg./g., to 61.1 mg./g., corresponding to an evaporation loss of only 7%.

EXAMPLE 4 A preservative formulation (F) was prepared from 2. 4,6-trichlorophenol (3.7 parts by weight) and xylene (96.3 parts), and another one (G) from 2,4,6-trichlorophenol (3.7 parts), Primene 8l-R dichromate (7.5 parts), and xylene (88.8 parts). Pinewood strips were impregnated with these two formulations, dried at the ordinary temperature, and samples analysed for their trichlorophenol content by the same method as was used for pentachlorophenol, all as in Example 1.

The strips were placed in an air oven at 50 C., and kept there for 1 week. At the end of this time the trichlorophenol content of the F-treated strips had fallen from its initial value of 21.3 mg./g., of wood to zero, corresponding to an evaporation loss of whereas in the case of the G-treated strips the initial trichlorophenol content of the wood remained unchanged at 22 mg./g., corresponding to zero evaporation loss.

Some of the G-treated strips, after keeping for 1 week at 50 C., were extracted 25 times with warm water in a Soxhlet extractor, when the trichlorophenol content of the wood fell from 22.0 mg./g., to 11.0 mg./g. Some of the F-treated strips, with no aging at 50 C., were extracted with warm water in exactly the same way, when the trichlorophenol content of the wood fell from 21.3 mg./g., to zero.

We claim:

1. A process for preserving woody cellulosic materials of wood, plywood, chipboard or hardboard, which comprises applying to the material an organic solvent soluion containing (i) from 0.5 to 10% by weight of a chlorinated phenol having one or more hydroxy groups bound to a benzene ring and from 1 to 5 chlorine atoms bound to the same benzene ring which is optionally substituted by one or more hydrocarbon groups or a salt of such a phenol soluble in the solvent, and (ii) from 1 to 50% by weight of a salt of chromic acid with an organic base which contains at least one straight or branched chain containing at least 6 carbon atoms, said salt having a solubility in the solvent sufficient to provide a solution containing at least 0.2% w./v. CrO (equivalent) at 20 C.

2. A process according to claim 1 wherein the chlorinated phenol and the salt of chromic acid are applied to the woody cellulosic material from the same solution.

3. A process according to claim 1 wherein the chlorinated phenol and the salt of chromic acid are applied to the woody cellulosic material from separate solutions.

4. A process as claimed in claim 1 wherein the chlorinated phenol or salt thereof contains from 3 to 5 chlorine atoms in the same benzene ring as the hydroxyl group.

5. A process as claimed in claim 6 wherein the chlorinated phenol employed is selected from the group comprising trichlorophenol, tetra chlorophenol, penta chlorophenol and mixtures thereof.

6. A process as claimed in claim 1 wherein the salt of chromic acid employed is a salt of a secondary tertiary alkyl primary amine having from 6 to 22 carbon atoms.

7. A process as claimed in claim 6 wherein the chromic acid salt employed is a salt of an amine selected from the group comprising 2-ethyl-n-hexyl amine, di(2-ethy1-nhexyl) amine, tri(3,5,5 trimethyl-n-hexyl) amine, a mixture of tertiary alkyl primary amines containing from 12 to 14 carbon atoms, a mixture of tertiary alkyl primary amines containing from 18 to 22 carbon atoms and a mixture of secondary alkyl primary amines derived from nundecane.

8. A process as claimed in claim 1 wherein there is also applied to the woody cellulosic material a biocidal copper" \arsenieorlgi grganotin compound. v

9. A process as claimed in claim 1 wherein said organic solution comprising a chlorinated phenol selected from the group comprising tri, tetra and penta chlorophenols and their solvent soluble salts and a salt of chromic acid with an amine selected from the group comprising 2-ethyln-hexyl amine, di(2-ethyl-n-hexyl) amine, tri(3,5,5-trimethyl-n-hexyl) amine, a mixture of tertiary alkyl primary amines containing from 12 to 14 carbon atoms, a mixture of tertiary primary amines containing from 18 to 22 carbon atoms and a mixture of secondary alkyl primary amines derived from n-undecane.

10. A process as claimed in claim 7 wherein said organic solvent solution contains from 1 to 25% of said chromic acid salt.

7 8 References Cited FOREIGN PATENTS UNITED STATES PATENTS 799,652 11/1956 Great Britain 106-14 3,234,085 2/1966 Renckhoft 117147 2,402,961 7/1946 Hill 106-15 AF 5 MURRAY KATLPnmaYY Examm" 2,035,527 3/1936 Brown 106-15 AF W. R. TENOR, Assistant Examiner 3,427,186 2/1969 Hudson 217 3,197,272 7/1965 Regutti 21--7 US. Cl. X.R. 2,314,362 3/1947 Mills 117-147 3,266,985 8/1966 Swales 117' 147 10 21 1O6 14' 15 3,535,167 10/1970 Ridder et a1. 10614 1;u':=..-.n'i.f;n. 3,702,]84 D d Novmber 14, 1972 i Inv mtofls) RQ HAR t It 1s ccrtitied that error appears in the. above-identificd patent and tnaf. 521d Letters Patent are hereby corrected as shown below:

Column 6, line 46, after "secondary" insert --or-.

Signed and sealed this 13th day of Mar ch 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

